Missing Intervals

Given a sorted array A[] of N distinct integers from 0 to 99999. Find all the integer intervals missing from the given list.

Note: There is always atleast 1 number missing.

• Time : O(n)
• Space : O(n)

class Solution {
public:
    vector<int> printMissingIntervals(int a[], int n) {
        vector<int> res;
        int last = -1;
        for (int i = 0; i < n; i++) {
            if (a[i] != last + 1) {
                res.push_back(last + 1);
                res.push_back(a[i] - 1);
            }
            last = a[i];
        }
        if(last != 99999) {
            res.push_back(last + 1);
            res.push_back(99999);
        }

        return res;
    }
};